Electric stove control



March 11, 1947.

lA. R. lVISITACION ELECTRIG STOVE CONTROL Filed Aug.v 3, 1946 V ATTORNEY INVENTOR f ANICETO R. VISITACION 01 n WMV Patented Mar. 11, 1947 i UNITED STATES PATENT OFFICE ELECTRIC STQVE CONTROL Aniceto R. Visitaclon, New York, N. Y.' Application Amst 3, 1946, Serial No. 688,327 3 Claims. (Cl. 212-37) vice under the control of the utensil supported on the heating unit, so that no current is permitted to ow to produce heat unless the utensil is placed on the device.

Other objects and advantages of the present invention will become apparent from the lfollowing specification and drawings showing a preferred embodiment of the invention, wherein Figure l is a perspective elevation view of a single unit stove incorporating the present invention;

Figure 2 is an elevational cross-sectional view of the control switch unit of the present invention, viewed on line 2-2 of Figure 3;

Figure 3 is a similar elevational cross-'sectional view of the device of Figure 2, viewed along line 3-3 thereof;

Figure 4 is a fragmentary elevational view of a portion of Figure 3, viewed along line 4-4 thereof and showing the stop arrangement for the switch;

Figure 5 is a diagrammatic representation of the switch drum and contacts, showing their relationship for the different switch positions;

Figure 6 is a schematic wiring diagram of the electrical circuit ofthe invention.

Referring to the drawings, the invention is illustratedas applied to a single-heater electric hot plate, although it will be understood that it is equally applicable to any number of units, as in a multi-unit electric range, each unit being provided with one of the control switch devices described herelnbelow.

Figure l shows a conventional one-unit electric hot-plate provided with the control switch de. vice of the present invention. The hot plate includes a stand I I carrying a two-filament heater I2 having a low resistance (high heat) fila- -ment I3 and a high resistance (low heat) lament I4 supported in grooves in a refractory disc 2D.

In use, a low level of heat is produced by energizing filament I4 alone, a medium level by en ergizing filament I3 alone, and a high heat level is produced by energizing both filaments I3 and I4 simultaneously. The heat level (or oi condition) is selected by a selector knob I5 having a pointer I6 cooperating with indicia I1 supported on the stand I I. Knob I5lis coupled by a shaft i8 to the control switch unit shown in more detail in Figures 2 to 4.

Projecting up through the center of the heater I2 for a Short distance (13; to 1%; inch) is the tip of a plunger I9 which normally maintains both filaments I3 and I4 de-energized until pressed downward by the weight of a utensil placed on the stove to be heated thereby. When depressed, plunger I9 permits the heater i2 to be energized to the level set by selector knob it. In this Way considerable electrical energy can be saved (since current ows only when heat is desired) and the inconvenience of using a separate switch for turning current on and o is avoided. Also, as will be seen, the level of heat desired can be set by knob I5 and left adjusted, with no current flow until plunger I9 is depressed.

The details of the switch control unit permitting the above-described operation are shown in Figures 2 through 6. ,The switch unit comprises an insulating housing 2l y preferably integrally molded, as of porcelain, which encases and supports lthe switch elements. Housing il is hung from stand Il by a flat-top bolt 23 which passes through aligned central openings in heater i2, the top surface 22 of stand il, and the top of housing 2I, and is held by a cooperating nut 2d. Bolt 23 is centrally bored to slidably receive plunger I9, which is terminated inan insulating tip 26, formed, for example, of molded porcelain.

A pair of opposed side walls 2l, 23 of housing i 2| are formed with aligned slots 29, 3U extending equal distances up from their bottom edges and adapted to receive switch shaft i8. Shaft i8 is retained in position substantially at the top of slots 29, 30 by a base plate 3l having a pair of upwardly extending lugs 32 fitting into slots 29, 3B with flat upper edges bearing against and supporting shaft I8. Plate 3| is removably fastened to housing 2| in any convenient fashion, as by screws 32. If plate 3I is metallic, an insulator plate 34 may be interposed between it and housing ,2l to prevent accidental short circuit.

Rigidly xed to shaft I8 is a switch drum having a substantially cylindrical insulating portion 36 xed to shaft I8 in any suitable manner and.

a sheet-metal conductor portion 31 supported on and overlying part of the drum insulator 3G.

Drum conductor 31 has a cylindrical portion 38` at one end to which are integrally connected three axially extending conductor strips 39, l0,

` grooves in drum insulator 36. As shown in Figures 2 and 5, strip 40 is spaced l45 degrees from strip 39, and strip 4| is spaced 90 degrees from strip 40. Also, halfway between strips 40 and 4| a detent groove 42 is formed in drum insulator 36, extending parallel to the drum conductor strips 39, 40,.4|. A similar detent groove 43 is formed on drum insulator 36 spaced 45 degrees from conductor strip 4|.

Cooperating with drum conductor strips 39, 4l), 4| are a pair of spring brushes 44, 46 supported from housing 2l by screws 4l and having crimped ends forming V contacts cooperating with the drum conductor strips 3S, 40, 4|, which are preferably formed with external grooves serving as detents for brushes 44, 46, as seen in Figure 2.

Aligned above the drum conductor cylinder 3E and normally spaced therefrom is a contacter 53 carried by a cantilever leaf spring 54 having one end fixed to housing 2l by a screw 56. Spring 54 is also aligned with tip 26 of plunger i9, and normally keeps plunger i9 extending above the top surface of heater i2, while maintaining contactor 53 away from drum conductor cylinder 38. Contactor 53 is connected by spring 56 and a wire l to one conductor of a cable 52 and thence to one terminal of a conventional two-prong plug 5i. l

When plunger i9 is depressed by the weight of a utensil placed upon heater i2, spring 5i is bent downward by plunger tip i9 and contacter 53 touches drum conductor cylinder Sdto complete the circuit from plug '5i to drum conductor 3l. Of course, as soon as the utensil is removed, spring 54 at once elevates plunger i@ to its former position and breaks contact between drum cylinder Se and contacter 53. Since contactor 53 is in the main supply circuit for the entire device, it maintains the heater inoperative, no matter what the setting vof knob i5 may be, so long as plunger i9 is not depressed.

As shown in Figure 6, brush 44 is connected by a wire le to one end of low-resistance heater iilament i3. Similarly, brush 46 is connected by a wire 49 to one end of high-resistance heater filament i4. The other ends of filaments i3 and i4 are connected together to the other conductor cable 52 and thence to the other terminal of plug 5|.

Figure 5 shows most clearly how brushes 44, 46 and drum conductor strips 36, 46, 4i cooperate to provide a four-position control (low, medium, high," and oii) for the electric stove. In this figure, brushes 44 'and 46 are shown schematically, while the drum contactor strips 39, 46, 4i are shown in cross-section, viewed similarly to Figure 2. Detent grooves 42 and 43 are also v shown.

In the upper view of Figure 5, knob [151s turned to the leftmost position, where brushes 44 and 46 |3 and i4 are connected to drum conductorv31, I

and both are energized when plunger i9 is depressed. This is the high position.

In the third view shown in Figure 5, knob l5 has been turned 45 degrees more, to the medium setting. Now brush 44 contacts strip 39 while brush 46 lies in detent groove 42 and is thus open-circuited. Hence only low-resistance iliament I3 is in the circuit, corresponding to medium heat. This is the position shown in Figures 2 and 3.

Similarly, in the lowest view of Figure 5, knob 45 has been turned 45 degrees more to the low position, and brush 44 isopen-circuited, while brush 46 is connected to strip 40, thereby connecting high-resistance filament i4 in the circuit to provide low heat. Thus the four positions of knob I5 and drum 3l provide 0ff, high medium and low control.

To provide an end-wise stop to keep drum 3l in proper axial position relative to brushes 44, 46 and contactor 53, and simultaneously to provide 'a rotary stop, the free end of shaft i8 is bent around as shown at 6i in Figure 4. This bent end 6| cooperates with slanted surfaces 62 formed on housing 2| to permit only approximately 180 degrees of rotation of shaft it. Since the four positions of drum 3l require only 135 degrees of angle, this rotary stop arrangement permits full use of the device, while preventing undesired connections which might be produced by further ro tation of drum 3l. The three additional positions of shaft i6 are shown in dotted lines in Figure 4, to indicate their relation to stop surfaces 62.

Accordingly, as described above, the present invention provides an extremely simple combined utensil-actuated and multiple-position manually actuated switch for electric hot plates or the like. However, the scope of the invention is indicated only by the appended claims and is not to be limited by the purely illustrative embodiment described in detail above.

I claim:

1. An electric s'tove apparatus comprising a heater element having a pair of independent heater filaments mounted on a refractory plate having a central aperture, a rotatable conductor drum having a completely cylindrical portion at one end thereof and three conductor strips axially extending therefrom toward the other end, a spring, a contacter supported on said spring opposite said cylindrical portion and adapted to close contact with said cylindrical portion upon ilexure of said spring, a plunger extending through said plate aperture to slightly above said plate and operatively positioned relative to said spring to flex 'said spring to make contact between said drum cylindrical portion and said contactor upon depression of said plunger, as by a utensil placed upon said plate, a pair of brushes disposed opposite said drum. conductor strips and adapted to contact one or both of said strips upon proper orientation of said drum, said brushes being connected respectively to one end of each of said filaments, the other ends of said filaments being connected together and to an input terminal and a second input terminal being connected to said spring, whereby said contactor and cylindi...al portion serve as a cut-off switch for said filaments, and said brushes and conductor strips` serve as a selector switch for connecting one or the other or both said filaments to said input terminals.-

2. An electric stove apparatus as in claim l wherein said brushes are spaced degrees apart around said drum and wherein one of said strips is spaced 45 degrees from a second strip on one side of said one strip and 90 degrees from the third strip on the other side of said one strip, whereby, upon successive rotations of s-aid drum through 45 angles, one filament, the other nlawith said plate aperture and through which said ment, both filaments, and neither iilament, are plunger extends, and fastening means passing successively connected to said input terminals. through said plate and housing apertures for 3. An electric 'stove apparatus as in claim 1 joining the same, said last means being centrally further including an .insulating housing sur- 5 bored to receive said plunger.

rounding said spring, contactor, drum, and

brushes, and having an upper aperture aligned ANICETO R.. VISITACION. 

